Studies will continue on the relation of the Epstein-Barr virus to certain malignant and non-malignant diseases. Efforts are being made to differentiate additional, EBV-coded antigens, to develop assays for cell-mediated immune responses specific for EBV-infected or EBV-transformed cells, to improve sources of various antigens for extraction and purification and to localize the cellular site of antigen synthesis at the ultra-structural level of immunoelectron microscopy. Established and emerging new techniques for detection of EBV-specific humoral or cell-mediated immune responses will be applied to continuing studies on EBV-associated diseases; i.e., infectious mononucleosis (with emphasis on its pathogenesis), Burkitt's lymphoma and nasopharyngeal carcinoma (in a search for further evidence for the role of EBV in the genesis of these tumors). Further work is planned also to assess the effects of immunosuppressive diseases or immunosuppressive therapy on the latent persistent Eb viral carrier state which is regularly established in the course or primary infections. BIBLIOGRAPHIC REFERENCES: Surface marker characteristics and Epstein-Barr virus studies of two established North American Burkitt's lymphoma cell lines. A.L. Epstein, W. Henle, G. Henle, J.F. Hewetson and H. S. Kaplan. Proc. Nat. Acad. Sci. (USA)73:228-232, 1976. Clinical and laboratory evaluation of elderly patients with heterophil-antibody positive infectious mononucleosis - report of seven patients, ages 40-78. C. A. Horwitz, W. Henle, G. Henle, M. Segal, T. Arnold, F.B. Lewis, D. Zanick and P. C. J. Ward. Am. J. Med. 61:333-339, 1976.